Determining value of mineral rights

I'm trying to estimate the value of mineral rights I inherited in 2013 for the purpose of calculating capital gains tax. Any suggestions on where/how I can find information like that?

Thanks

Joe

Use your worksheet from the Estate you inherited. There is a ratio your CPA can use to determine tax.

Not sure what you mean by worksheet. There was no value attached to the inheritance. My CPA is saying they can't find a good resource for value estimation. They don't want to underestimate value at time of inheritance but it obviously wasn't zero so it's a tough call.